Arming and firing circuit



p 9 D. D. AULDS ETAL 3,343,493

ARMING AND FIRING CIRCUIT Filed Jan. 11, 1966 zavo'c POWER SUPPLYINVENTOR8 DARRELL D. AULDS HAROLD R. SOHE/BE, JR.

ATTORNEY United States Patent 3,343,493 ARMING AND FIRING CIRCUITDarrell D. Aulds, Ruston, La., and Harold R. Scheibe, J12, King George,Va., assignors to the United States of America as represented by theSecretary of the Navy Filed Jan. 11, 1966, Ser. No. 520,316 6Claims.'(Cl. 102-70.2)

ABSTRACT OF DISCLOSURE The specification and drawing disclose a timedelay fail-safe firing system utilizing two SCRs and a capacitordischarge firing circuit to enable the SCRs. The firing circuit isinitiated when the power and ground circuits are broken thereby causingthe capacitor to discharge through the gate circuit of the SCR and thencausing the SCR to conduct and thereby detonate the load.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

The present invention relates to firing circuits for electronic fuzesystems and in particular to timing circuitry employing semi-conductordevices to provide a safe, compact and reliable circuit for the purposeintended.

More specifically, the invention relates to an ignition circuit fordetonating explosives in which a predetermined time delay may beproduced between the disconnection of the circuit from the relatedelectrical system and the detonation of the explosive charge.

Such a circuit would, for example,be incorporated with a positivedestruct system in aircraft equipment that is designed to be jettisonedor dropped while in flight such that at a predetermined time afterjettisoning the circuit will detonate the explosive charge associatedtherewith.

The description of the use is for illustrative purposes only and it willbe understood that such a circuit is readily adaptable for use with anyload that would require a signal at a predetermined time after thecircuit was disconnected from the associated electrical system.

Such a circuit must be compact and as efiicient as possible due to thesevere space limitations and the high reliability requirements imposedby the aircraft environment. It is also desirable that such a circuitwill not be susceptible to stray electromagnetic radiation which mightaccidentally detonate the associated explosive charge and that thecircuit will drain very little current from the associated electricalsystem.

Accordingly, it is an object of the present invention to provide anelectrical circuit capable of producing a time lag of the aforesaidnature. I

Another object of the present invention is to provide an electricalcircuit capable of producing a signal at a predetermined time after thecircuit has been disconnected from the associated power supply andelectrical grounds.

A further object of the present invention is to provide an electricalcircuit for use with electronic fuze systems and which circuit willproduce a time lag of the aforesaid nature.

Still another object of the present invention is to provide a new andimproved circuit for use with a fuze system which will produce apredetermined time delay between the initiating occurrence and thedetonation of the explosive charge that is associated with the fuzesystem.

Yet another object of the present invention is the provision of a firingcircuit for use with electronic fuze 3,343,493 Patented Sept. 26, 1967systems which circuit is not susceptible to stray electromagneticradiation which might accidentally detonate the associated explosivecharge.

Still a further object of the present invention is to provide a firingcircuit which will have a low current drain on the electrical system inwhich it is connected.

Other objects, advantages and novel features of the present inventionwill become apparent from the following detailed description of theinvention when considered in conjunction with the accompanying drawingwheren:

The figure shows a schematic of the circuit of the present inventionwith the associated casing.

Referring now to the drawing in detail, the ground 10 is-electricallycoupled to the cathode of Zener diode 12 via the positive plate of afirst feed through capacitor 14, diode 16 and resistor 18. The 28 voltdirect current power supply or potential source means 20 is electricallycoupled to the anode of a first silicon controlled rectifier 22 via thepositive plate of a second feed through capacitor 24, diode 26 andcurrent limiting resistor 30. The anode of Zener diode 12 iselectrically coupled to one terminal of plug 32 via resistors 34, 36 andis also electrically connected to the control gate of the first siliconcontrolled rectifier 22. A lead 38 electrically connects a secondterminal of plug 32 with ground 40. The anode of the first siliconcontrolled rectifier 22 is electrically connected to the anode of asecond silicon controlled rectifier 42 and to the positive plate offiring capacitor 44. The negative plate of firing capacitor 44 iselectrically connected to ground 40 via lead 38. The cathode of thefirst silicon controlled rectifier 22 is electrically connected to thecontrol gate of the second silicon controlled rectifier 42 and also 'tothe line between resistors 34 and 36. The cathode of the second siliconcontrolled rectifier 42 is electrically connected to the same line andthe same terminal of plug 32 as the anode of Zener diode 12.

A resistor 46 is electrically connected between the cathodes of diodes16 and 26. The negative plate of timing capacitor 48 is electricallyconnected to the cathode of Zener diode 12 via resistor 18. The positiveplate of timing capacitor 48 is electrically connected to the cathode ofZener diode 12 via potentiometer 50 and is also electrically connectedto the anode of silicon controlled rectifier 22. The timing capacitorand potentiometer 50 form a network means for producing a time lag ofpredetermined duration as will hereinafter be described. A two polesingle throw switch 52 electrically grounds, when closed, the positiveplate of firing capacitor 44 and both the anode and cathode of thesecond silicon controlled rectifier 42 such that the circuit isincapable of operation and thus acts as an arm-safe switch.

The entire circuit is shown in case 56 which together with feed-throughcapacitors 14 and 24 acts 'as a filter means to eliminate any strayelectromagnetic radiation from affecting the circuit. The negativeplates of feedthrough capacitors 14 and 24 are shown attached to thecase 56 and with the case 56 grounded at 40 via connection at 58. Theleads extending beyond casing 56 to plug 32 are encased in shieldedcable which is grounded to the casing 56 as indicated at 60.

The plug 32 is shown connected to a detonator 62 for illustrativepurposes only and it will be obvious that the circuit of the presentinvention could be employed with any load which requires a signal orneeds to be controlled at a determined time after the circuit has beendisconnected from the power supply means.

In operation the application of power supply means 20 with the switch 52in armed or open position will charge the positive plate of timingcapacitor 48 and the positive plate of firing capacitor 44. After thecapacitors 48 and 44 are charged, the only source of continuous currentdrain will be through resistor 46 since potentiometer 50 will be almostan open circuit due to its large ohmic value in comparison to resistors30 and 46, and the circuit will therefore be in a ready state. If thecircuit is now disconnected from the power supply means 20 and groundsand 40, the positive plate of capacitor 48discharges at a predeterminedtime rate, through potentiometer 50 until the potential across Zenerdiode 12 has risen to a predetermined value due to the negative plate ofcapacitor 48 becoming more positive, at which time the Zener diode 12conducts and places a voltage on the control gate of the first siliconcontrolledrectifier 22. Rectifier 22.then conducts and places a voltageon the control gate of the second silicon controlledrectifier 42 thusallowing'the second rectifier42 to conduct. With the: secondsiliconcontrolled rectifier 42 conductive, the firing capacitor 44discharges through the rectifier 42 and actuates the squib of detonator62. The explosive system isthus set off after a predetermined timedelay. The cir-- cuit may be disarmed by simply turning off the powersupply. from the circuit, while leaving grounds 10 and 40 connected,whereby the capacitors-44 and 48-are discharged through resistors and46. to ground 10. If switch 52 is closed orin the safe position, thefiring capacitor 44 will not be charged and the circuit will beincapable of accidentally actuating detonator 62.

While applicants-do not wish to be limited to any particular set ofcircuit constants, the following constants;

have proven to be useful in the'particular circuit shown.

Capacitors 14, 24 6.8 microfarads. Diodes 16, 26 GE type 1N538. Resistor46 1 kilohm. Resistors 18, 30 270 ohms. Capacitor 48' 220 microfarads.Potentiometer 50 25 kilohms. Zener diode 12 GE type 1N1771A. Siliconcontrolled rectifier 22 GE type 2N2323. Silicon controlled rectifier 42GE type C40F. Capacitor 44 4000 microfarads. Resistor 34- 4.7 kilohms.Resistor 36 15 kilohms.

Obviously many. modifications and variations of the present inventionare possible in light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims. the inventionmay. be practiced otherwise than as specifically described.

What is claimed is:

1. A circuit for controlling. a loadcomprising electrical ground means;

a firstand'a second silicon, controlled rectifier, each of saidrectifiers having an anode, a cathode anda control gate, said cathode ofsaid firstrectifier connectedto said gate of said second rectifier, theanodes of said first'and second: rectifiers electrically.

coupled to said ground means;

a firing capacitor electrically'connected to said anode of said secondrectifier;

a Zener diode electrically connected to said control gate of said firstrectifier;

a resistance-capacitance network means electrically connected inparallel betweensaid Zener diode and saidanode of said first rectifier;

a potential source means electrically coupled to said circuit forcharging both the capacitance of said network means and said firingcapacitor whereby if the circuit is disconnected from both saidpotential source means and said electrical ground means the capacitancedischarges through the resistance of said network means and causes saidZener diode to conduct after a predetermined time lag which in turnallows the first and second rectifiers to conduct and thus permits thefiring capacitor to discharge through said second rectifier to a load tobe controlled.

2. A circuit as described in claim 1 wherein said network means includesa timing capacitor having a positive and a negative plate, the positiveplate being charged by said potential source means whereby thedisconnection of said circuit from said potential source means allowsthe positive plate of said timing capacitor to discharge through theresistance of said network means to allow the Zener diode to conduct.

3. A circuit as described in claim 1 for use in an electronic fuzesystem having a detonator wherein:

said Zener diode includes an anode and a cathode, the anode beingelectrically coupled to the control gate of said first rectifier; and

said network means includes a, timing capacitor and a potentiometer,said timing capacitor having a positive and a negative plate, both saidtiming capacitor and said potentiometer being electrically coupled inparallel between the anode of said first rectifier and the cathode ofsaid Zenerdiode, said positive plate of said timing capacitor beingcharged by said potential source means whereby the disconnection of saidcircuit from said potential source means and said electrical groundmeans allows said positive plate to discharge through said potentiometerto make said Zener diode conductive and which ultimately results in saidfiring. capacitor discharging through said second silicon controlledrectifier to said detonator of said fuze system.

4; A circuit as described in claim 3 including a switch electricallygrounding said firing capacitor and said cathode of said secondrectifier when said switch is closed.

5. A circuit as defined in claim 3 including filter means ReferencesCited- UNITED STATES PATENTS 4/1965, Urban 30788.5

8/1965 Carrol 30788.5

BENIAMIN A. BORCHELT, Primary Examiner..

W. C. ROCH, Assistant Examiner.

1. A CIRCUIT FOR CONTROLLING A LOAD COMPRISING ELECTRICAL GROUND MEANS;A FIRST AND SECOND SILICON CONTROLLED RECTIFIER, EACH OF SAID RECTIFIERSHAVING AN ANODE, A CATHODE AND A CONTROL GATE, SAID CATHODE, OF SAIDFIRST RECTIFIER CONNECTED TO SAID GATE OF SAID SECOND RECTIFIER, THEANODES OF SAID FIRST AND SECOND RECTIFIERS ELECTRICALLY COUPLED TO SAIDGROUND MEANS; A FIRING CAPACITOR ELECTRICALLY CONNECTED TO SAID ANODE OFSAID SECOND RECTIFIER; A ZENER DIODE ELECTRICALLY CONNECTED TO SAIDCONTROL GATE OF SAID FIRST RECTIFIER; A RESISTANCE-CAPACITANCE NETWORKMEANS ELECTRICALLY CONNECTED IN PARALLEL BETWEEN SAID ZENER DIODE ANDSAID ANODE OF SAID FIRST RECTIFIER; A POTENTIAL SOURCE MEANSELECTRICALLY COUPLED TO SAID CIRCUIT FOR CHARING BOTH THE CAPACITANCE OFSAID NETWORK MEANS AND SAID FIRING CAPACITOR WHEREBY IF THE CIRCUIT ISDISCONNECTED FROM BOTH SAID POTENTIAL SOURCE MEANS AND SAID ELECTRICALGROUND MEANS THE CAPACITANCE DISCHARGES THROUGH THE RESISTANCE OF SAIDNETWORK MEANS AND CAUSES SAID ZENER DIODE TO CONDUCT AFTER APREDETERMINED TIME LAG WHICH IN TURN ALLOWS THE FIRST AND SECONDRECTIFIERS TO CONDUCT AND THUS PERMITS THE FIRING CAPACITOR TO DISCHARGETHROUGH SAID SECOND RECTIFIER TO A LOAD TO BE CONTROLLED.